A significant fraction of resting T-cells derived from old mice when polyclonally activated failed to complete the Gl phase of the cell cycle and underwent apoptotic cell death. The transcription of several genes known to be critical during the G1 phase was shown to be significantly reduced in the activated T-cells of the old mice. In situ hybridization data showed a reduction in the number of positive cells as well as reduced level of specific mRNA being produced in the responsive cells from the old mice. Activated T-cells blocked late in Gl expressed normal levels of specific mRNA for transferrin receptors, IL-2 and IL-2R alpha and beta as well as the corresponding proteins. The blocked cells were however unable to maintain normal levels of specific mRNA for c-myc and cdk2 and there was no detectable cdc2 mRNA. The presence of c-myc antisense during the activation process also inhibited the expression of cdc2 and cdk2 and the activated T-cells failed to traverse Gl/S indicating a role for c-myc in the Gl that involves the transcriptional regulation of the cyclin dependent kinases.